The present invention relates generally to resonant power conversion systems. More particularly, the present invention relates to a multiphase LLC DC-DC power converter with both active and passive internal current sharing.
Current requirements for high efficiency (e.g., greater than 94%) in AC/DC power supplies with a 12 volt output has resulted in the common use of parallel power stages/power trains to minimize current stress in each power train and the output of the power supply unit. For best performance and reliable operation, different active or passive current sharing methods have been implemented in the past.
To further improve performance and power density, and especially also to achieve flat efficiency curves across the load range, new solutions have been implemented in recent years, including for example using more than two power trains with active phase shedding (dynamic turning on/off of phases). It is critical to control the current in each phase since a single phase (e.g., one of N total phases) can typically only handle slightly more than 1/N of the overall power. With systems having an increased number of phases (N), this problem becomes even more pronounced.